gEDA-user: Slotting

[John Doty <jpd@xxxxxxxxx>]

The current implementation of slotting in gEDA is confusing and  
inflexible.

It overloads the pinseq= attribute, which is also used to order pins  
for SPICE netlisting.

It does not work when the slots are heterogeneous. This, in turn,  
either requires hidden power pins or redundant power pins if the user  
wishes to employ this mechanism to break down a slotted chip. Even if  
the slots are homogeneous, the designer may wish to use heterogeneous  
graphics for a single chip, e.g. NOR and IAND logic.

The approach of getting around the slotting limitations by giving the  
same refdes to several instances of different symbols works fine, but  
users are dissatisfied with it. It's clumsy and does not lend itself  
well to automatic checking.

I propose a new attribute, slotfile. An example might be  
"slotfile=2,dualopamp-2.1.slot" (the 2 refers to slot 2). The slot  
file format would be the same as a symbol, but "ultralight", with  
only graphics, pins, and attributes attached to pins. The slotfile=  
attribute would go into a symbol file, along with the usual other  
stuff. gschem and gnetlist would combine the data from the slot file  
with the data from the symbol to draw and connect the instance.

An extended slot numbering syntax (e.g. "2.2") could be used to  
select alternative graphics for a slot.

The old mechanism could be left in place. Many, including me, would  
scream if it changed. If the slot is defined by slotdef=, it's old  
style, by slotfile=, it's new style.

I think this is a minimally invasive change that will make the slot  
mechanism more flexible and easier to understand.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user